Legal analysis: the contract and receipt need not be returned when the refund is made, and the payee can be required to issue the receipt of the refund as a legally binding certificate.

Legal basis: Article 63 of the Civil Procedure Law of People's Republic of China (PRC) includes:

(a) the statement of the parties; (2) Documentary evidence; (3) Physical evidence; (4) Audio-visual materials; (5) Electronic data; (6) Testimony of witnesses; (7) Expert opinions; (8) Inspection records. Evidence must be verified before it can be used as a basis for ascertaining facts.